Image processing apparatus, image displaying apparatus, and image processing method

ABSTRACT

An image processing apparatus for correcting image signals corresponding to a plurality of color images constituting an image, includes: a correction table storage unit storing one or more correction tables; and an image signal correcting unit independently correcting the image signals of the color images on the basis of one or more correction tables stored in the correction table storage unit, wherein the image signal correcting unit makes a geometric correction of a display image corresponding to the image such that display color images each corresponding to the color images superpose each other, independently among the color image.

BACKGROUND

1. Technical Field

The present invention relates to an image processing apparatus, an imagedisplaying apparatus, and an image processing method.

2. Related Art

A projector as an image displaying apparatus (image projectingapparatus) can be installed easily and can display a large-sized imageat low cost, which could not be obtained by liquid crystal displays. Theprojector projects an image onto a screen. Accordingly, when thepositional relation between the projector body and the screen ischanged, a characteristic of the projector is that the shape of adisplay image is changed. For this reason, recent projectors correct theshape of a display image, which is changed depending on the positionalrelation between the projector body and the screen, by making ageometric correction such as a keystone correction as an imagingprocess.

The projector displays a large-sized image by making light from a lightsource (lamp) incident on a light modulating device, synthesizing orextending and projecting an image by the use of an optical system, andfocusing the image on the screen. The color of a display pixel on thescreen corresponding to one pixel is expressed by superposing displaysub pixels corresponding to plural sub pixels of primary colorcomponents. Accordingly, a phenomenon (pixel shift) that the displaypositions of the display sub pixels of the color components are shiftedfrom each other occurs due to an installation precision of the lightmodulating device, an influence of temperature on expansion andcontraction, chromatic aberration of components of the optical system,or the like, thereby deteriorating the image quality.

Therefore, for example, JP-A-8-102901 discloses a technique of makingthe keystone correction and making a correction of the pixel shift. InJP-A-8-102901, the position of the image on a liquid crystal panel, asthe light modulating device, is shifted in parallel in the unit ofpixels by shifting the time points of horizontal and verticalsynchronization signals. By sequentially making the keystone correctionand adjusting the time points of the horizontal and verticalsynchronization signals, the keystone correction and the correction ofthe pixel shift are made.

However, in the technique disclosed in JP-A-8-102901, the parallel shiftof the image position on the liquid crystal panel is carried out only inthe unit of pixels and thus the deterioration in image quality due tothe pixel shift may not be satisfactorily suppressed. In the techniquedisclosed in JP-A-8-102901, a circuit for making the keystone correctionand a circuit for adjusting the time points of the horizontal andvertical synchronization signals are required, thereby enhancing thecircuit size and elongating the delay time of the imaging process.

SUMMARY

An advantage of some aspects of the invention is that it provides animage processing apparatus, an image displaying apparatus, and an imageprocessing method which, with a simple structure, can make a correctionof a pixel shift and a geometric correction.

According to an aspect of the invention, there is provided an imageprocessing apparatus for correcting image signals corresponding to aplurality of color images constituting an image, including: a correctiontable storage unit storing one or more correction tables; and an imagesignal correcting unit independently correcting the image signals ofcolor images on the basis of one or more correction tables stored in thecorrection table storage unit. Here, the image signal correcting unitmakes a geometric correction of a display image corresponding to theimage such that display color images each corresponding to the colorimages superpose each other, independently among the color image.

According to this configuration, since the image signals are correctedindependently among the color components on the basis of a correctiontable stored in the correction table storage unit and the geometriccorrection of the display image formed by the display pixels displayedby superposing the display sub pixels is made, it is possible to providean image processing apparatus capable of making a geometric correctionwith a simple structure without adjusting the time points of thehorizontal and vertical synchronization signals.

In the image processing apparatus, the correction table storage unit maystore a correction table including correction data corresponding to anamount of pixel shift in the display position of the display color imageand a geometric correction amount of the display image, and the imagesignal correcting unit may correct the image signals so as to make ageometric correction of the display image and corrects the pixel shiftto correspond to the amount of pixel shift.

According to this configuration, since the correction tables, includingthe correction data corresponding to the amount of pixel shift, and thegeometric correction amount are stored in the correction table storageunit, it is possible to make both correction of the pixel shift and ageometric correction with a simple structure. Accordingly, it is alsopossible to reduce the delay time of the image process.

In the image processing apparatus, the image signal correcting unit maycorrect the image signal of sub pixel constituting the color image tomake a geometric correction of the display image and correct the pixelshift by interpolating the image signal of the one sub pixel and theimage signals corresponding to one or more sub pixels around the one subpixel on the basis of the correction table.

According to this configuration, since the image signal of one sub pixeland the image signals corresponding to one or more sub pixels around theone sub pixel are interpolated on the basis of the correction tables, itis possible to provide an image processing apparatus capable of making acorrection of the pixel shift in a unit smaller than one pixel andmaking both a correction of the pixel shift and a geometric correctionwith a simple structure.

In the image processing apparatus, when one pixel is constructed by N(where N is an integer of 2 or greater) sub pixels, the correction tablestorage unit may store N types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels and thegeometric correction amount of the display image. In this case, theimage signal correcting unit may independently correct the image signalsamong the color image on the basis of the correction tables which differdepending on the color image.

According to this configuration, it is possible to provide an imageprocessing apparatus with a simple structure which is capable ofindependently making a correction among the N types of color components.Therefore, it is possible to simultaneously perform plural types ofcorrection processes such as the correction of the pixel shift and thegeometric correction on the respective color components.

In the image processing apparatus, when one pixel is constructed by N(where N is an integer of 2 or greater) sub pixels, the correction tablestorage unit may store (N−1) types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels. In thiscase, the image signal correcting unit may correct the image signals ofthe (N−1) types of color images independently.

According to this configuration, it is possible to provide an imageprocessing apparatus with a simple structure which is independentlycapable of making a correction among (N−1) types of color components.Therefore, with respect to the display position of the display sub pixelof one color component, it is possible to correct the pixel shiftcorresponding to the amount of pixel shift in the display position ofthe display sub pixels of the other color components.

In the image processing apparatus, when an image is displayed on acylindrical screen with a radius R by an image displaying apparatusdisposed backwardly apart by L from a point of view located at thecenter of the cylindrical screen, a correction table stored in thecorrection table storage unit may include correction data of an angle θby the use of the following expression,

${\Delta \; x} = {\frac{{R\left( {L + \sqrt{R^{2} - w^{2}}} \right)}\; {\sin \theta}}{{R\; {cos\theta}} + L} - {\sqrt{{R^{2} - w^{2}}\;}{tan\theta}}}$

where 2w represents the width in the horizontal direction of thecylindrical screen as viewed from the point of view and Δx representscorrection data for the sub pixel in the direction of the angle θ fromthe point of view.

According to this configuration, it is possible to provide an imageprocessing apparatus capable of making a geometric correction of animage projected onto the cylindrical screen at the same time ascorrecting the pixel shift with a simple structure.

According to another aspect of the invention, there is provided an imagedisplaying apparatus for displaying an image on the basis of imagesignals corresponding to a plurality of color images constituting theimage, including: the above-mentioned image processing apparatus; and animage displaying unit making a display to superpose display color imagescorresponding to the color image on the basis of the image signalscorrected by the image processing apparatus.

According to this configuration, it is possible to provide an imagedisplaying apparatus capable of displaying an image suppresseddeterioration in image quality or having been subjected to the geometriccorrection by making a correction of the pixel shift or a geometriccorrection with a simple structure.

According to another aspect of the invention, there is provided an imageprocessing method of correcting image signals corresponding to aplurality of color images constituting an image, including: acquiringthe image signals corresponding to the color images; and independentlycorrecting the acquired image signals among the color images on thebasis of one or more correction tables stored in a correction tablestorage unit. Here, the correction of the image signals includes makinga geometric correction of a display image corresponding to the imagesuch that display color images each corresponding to the color imagessuperpose each other, independently among the color image.

According to this configuration, since the image signals areindependently corrected among the color components on the basis of oneor more correction tables stored in the correction stable storage unitand the geometric correction of the display image formed by the displaypixels displayed by superposing the display sub pixels is made for eachcolor component, it is possible to provide an image processing methodcapable of making a geometric correction with a simple structure withoutadjusting the time points of the horizontal and vertical synchronizationsignals.

In the image processing method, the correction table storage unit maystore a correction table including correction data corresponding to anamount of pixel shift in the display position of the display colorimages and a geometric correction amount of the display image. Here, thecorrection of the image signals may include correcting the image signalsso as to make a geometric correction of the display image and correctingthe pixel shift to correspond to the amount of pixel shift.

According to this configuration, since the image signals areindependently corrected among the color components on the basis of thecorrection tables including the correction data corresponding to theamount of pixel shift and the geometric correction amount, it ispossible to make both a correction of the pixel shift and a geometriccorrection with a simple structure. Accordingly, it is also possible toreduce the delay time of the image process.

In the image processing method, the correction of the image signals mayinclude making a geometric correction of the image signal of sub pixelconstituting the color image and correcting the pixel shift byinterpolating the image signal of the one sub pixel and the imagesignals corresponding to one or more sub pixels around the one sub pixelon the basis of the correction table.

According to this configuration, since the image signal of one sub pixeland the image signals corresponding to one or more sub pixels around theone sub pixel are interpolated on the basis of the correction tables, itis possible to provide an image processing method capable of making acorrection of the pixel shift in a unit smaller than one pixel andmaking, with a simple structure, both a correction of the pixel shiftand a geometric correction.

In the image processing method, when one pixel is constructed by N(where N is an integer of 2 or greater) sub pixels, the correction tablestorage unit may store N types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels and thegeometric correction amount of the display image, and the correction ofthe image signals may include independently correcting the image signalsamong the color image on the basis of the correction tables which differdepending on the color image.

According to this configuration, it is possible to provide an imageprocessing method capable of making an independent correction among theN types of color components with a simple structure. Therefore, it ispossible to simultaneously perform plural types of correction processessuch as the correction of the pixel shift and the geometric correctionon the respective color components.

In the image processing method, when one pixel is constructed by N(where N is an integer of 2 or greater) sub pixels, the correction tablestorage unit may store (N−1) types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels, and thecorrection of the image signals may include independently correcting theimage signals of the (N−1) types of color components among the colorimage.

According to this configuration, it is possible to provide an imageprocessing method capable of making an independent correction among(N−1) types of color components with a simple structure. Therefore, withrespect to the display position of the display sub pixel of one colorcomponent, it is possible to correct the pixel shift corresponding tothe amount of pixel shift in the display position of the display subpixels of the other color components.

In the image processing method, when an image is displayed on acylindrical screen with a radius R by an image displaying apparatusdisposed backwardly apart by L from a point of view located at thecenter of the cylindrical screen, a correction table stored in thecorrection table storage unit may include correction data of an angle θby the use of the following expression,

${\Delta \; x} = {\frac{{R\left( {L + \sqrt{R^{2} - w^{2}}} \right)}\; {\sin \theta}}{{R\; {cos\theta}} + L} - {\sqrt{{R^{2} - w^{2}}\;}{tan\theta}}}$

where 2w represents the width in the horizontal direction of thecylindrical screen as viewed from the point of view and Δx representscorrection data for the sub pixel in the direction of the angle θ fromthe point of view.

According to this configuration, it is possible to provide an imageprocessing method capable of making a geometric correction of an imageprojected onto the cylindrical screen at the same time as correcting thepixel shift with a simple structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram illustrating the configuration of an imagedisplaying system including a projector according to an embodiment ofthe invention.

FIG. 2 is a block diagram illustrating the configuration of an imageprocessor according to the embodiment in detail.

FIG. 3 is a diagram illustrating the configuration of a projection unit.

FIGS. 4A and 4B are diagrams illustrating a geometric correction processaccording to the embodiment of the invention.

FIG. 5 is a diagram schematically illustrating the shapes of a displayimage before and after the geometric correction according to theembodiment of the invention.

FIG. 6 is a diagram schematically illustrating a display pixelconstituting a display image projected onto a screen by the projectionunit shown in FIG. 3.

FIG. 7 is a diagram illustrating the operation of an R-componentcorrection amount calculating section shown in FIG. 2.

FIG. 8 is a diagram illustrating an amount of pixel shift in the displayposition of display sub pixels according to the embodiment.

FIG. 9 is a diagram illustrating the operation of an R-component imagesignal correcting section shown in FIG. 2.

FIG. 10 is a block diagram illustrating the hardware configuration of animage processor according to the embodiment.

FIG. 11 is a diagram illustrating an example where a correction tablestorage area is allocated in a first processing example.

FIGS. 12A and 12B are diagrams illustrating the correction in the shapeof an image projected onto a cylindrical screen.

FIG. 13 is a diagram illustrating a correction amount in FIG. 12B.

FIG. 14 is a flowchart illustrating processes of the image processor inthe first processing example according to the embodiment.

FIG. 15 is a diagram illustrating an example where a correction tablestorage area is allocated in a second processing example.

FIG. 16 is a diagram illustrating a correction amount of an R-componentpixel shift in the second processing example.

FIG. 17 is a flowchart illustrating processes of the image processor inthe second processing example.

FIG. 18 is a diagram illustrating an example where a correction tablestorage area is allocated in a third processing example.

FIG. 19 is a diagram illustrating a correction amount in the thirdprocessing example.

FIG. 20 is a flowchart illustrating processes of the image processor inthe third processing example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the accompanying drawings. The followingembodiments are not intended to unfairly restrict the details of theinvention described in the claims. All elements described below are notessential requirements of the invention.

Although a projector is exemplified as an image displaying apparatus(image projecting apparatus) according to an embodiment of the inventionin the following description, the image displaying apparatus accordingto the invention is not limited to the projector. For example, thedeterioration in image quality due to the shift of the display positionsof display sub pixels corresponding to sub pixels can occur in variousimage displaying apparatuses as well as the projector. Accordingly, theimage displaying apparatus according to the invention is not limited tothe projector.

FIG. 1 is a block diagram illustrating the configuration of an imagedisplaying system, including the projector, as the image displayingapparatus according to an embodiment of the invention.

The image displaying system 10 according to this embodiment includes aprojector 20 and a screen SCR. The projector 20 displays an image byprojecting modulated light onto the screen SCR on the basis of the imagesignals corresponding plural color components. Here, one pixel of aninput image includes plural sub pixels corresponding to plural colorcomponents. A display pixel constituting a display image projected ontothe screen SCR includes plural display sub pixels corresponding to theplural sub pixels constituting one pixel.

The projector 20 includes an image processor 30 as an image processingapparatus and a projection unit 100 as an image display unit.

The image processor 30 performs a geometric correction process (shapecorrecting process) of the display image projected onto the screen SCRon the image signals corresponding to pixel values of the sub pixels bycolor components (by sub pixels). The image processor can perform apixel shift correcting process corresponding to the amount of pixelshift in the display position of the display sub pixels constitutingeach display pixel in the display image at the same time as performingthe geometric correction process. The image signals are generated by animage signal generating device not shown and are supplied to the imageprocessor 30.

The projection unit 100 modulates beams from the light source by colorcomponents on the basis of the image signals corrected by the imageprocessor 30, synthesizes the modulated beams of the color components,and projects the synthesized beams onto the screen SCR so as tosuperpose the display sub pixels on each other. Accordingly, it ispossible to correct the shape of the image projected onto the screen SCRand to suppress the deterioration in image quality due to the pixelshift.

The image processor 30 includes a correction table storage unit 40, acorrection amount calculating unit 44, and an image signal correctingunit 46. The correction table storage unit 40 stores one or morecorrection tables. Each correction table includes correction datacorresponding to the correction amounts of the image signals of thecolor components. The correction amount calculating unit 44 calculatesthe correction amount of the image signal of the respective colorcomponents on the basis of the correction tables specified by colorcomponents out of the correction tables stored in the correction tablestorage unit 40. The image signal correcting unit 46 independentlycorrects the image signals using the correction amounts calculated bythe correction amount calculating unit 44 among the color components andmakes a geometric correction of the display image formed by the displaypixels displayed so as to superpose the display sub pixels correspondingto the sub pixels. The image signals having been subjected to thegeometric correction by the image signal correcting unit 46 are outputto the projection unit 100.

Here, when one pixel includes the sub pixels of N (where N is an integerof 2 or greater) color components, the correction table storage unit 40can store one or more correction tables and the first to N-thcorrections tables 42 ₁ to 42 _(N) in maximum are individually referredto at the same time. By employing correction data corresponding to theamount to be geometrically corrected, the amount of the pixel shift, andother amounts to be corrected as the correction data included in thecorrection tables, what correction table to refer to can be specifiedfor each color component and the image signal correcting unit 46 cansimultaneously perform plural correction processes on the image signalsof the color components.

For example, the correction table storage unit 40 stores a correctiontable corresponding to the amount of pixel shift of the display positionof the display sub pixels and the amount of geometric correction of thedisplay image formed by the display pixels and the correction amountcalculating unit 44 calculates the correction amounts on the basis ofthe correction table. The image signal correcting unit 46 corrects theimage signals so as to make a geometric correction of the display imageand corrects the pixel shift corresponding to the amount of pixel shift,on the basis of the correction amount calculated by the correctionamount calculating unit 44. Accordingly, without an individual geometriccorrection circuit and a pixel shift correcting circuit and withoutsequentially performing the correction processes, it is possible to makeboth a geometric correction and a correction of the pixel shift with asmall-sized configuration.

It is preferable that the correction tables stored in the correctiontable storage unit 40 include correction data on plural representativepixels (representative points) in one screen of the display image. Inthis case, the correction amount calculating unit 44 calculates thecorrection data of the sub pixel positions by the interpolation processusing the correction data of the correction tables. In this way, thecorrection amount calculating unit 44 can calculate the correctionamounts of all the pixels in one screen.

Although it will be described in the following that N is “3” and onepixel includes sub pixels of the R component, the G component, and the Bcomponent, this embodiment is not limited to the number of colorcomponents constituting one pixel.

FIG. 2 is a block diagram illustrating the detailed configuration of theimage processor 30 according to this embodiment. In FIG. 2, the sameelements as shown in FIG. 1 are referenced by the same referencenumerals and a description thereof is properly omitted.

The image processor 30 in this embodiment further includes a correctiontable selecting unit 50 and a correction process specifying unit 52, inaddition to the correction table storage unit 40, the correction amountcalculating unit 44, and the image signal correcting unit 46 shown inFIG. 1.

The correction table selecting unit 50 selects the correction tablespecified by the correction process specifying unit 52 for each colorcomponent out of the first to third (=N) correction tables 42 ₁ to 42 ₃stored in the correction table storage unit 40. The correction tableselecting unit 50 outputs the correction data of the specifiedcorrection table to the correction amount calculating unit 44 for eachcolor component.

The correction process specifying unit 52 specifies one of the first tothird correction tables 42 ₁ to 42 ₃ stored in the correction tablestorage unit 40 for each color component. The correction processspecifying unit 52 may specify a correction table common to plural colorcomponents or may specify correction tables different by colorcomponents.

The correction process specifying unit 52 specifies ON or OFF of acorrection process for each color component. The image signal of thecolor component of which the correction process is specified as ON issubjected to the correction process. The image signal of the colorcomponent of which the correction process is specified as OFF is notsubjected to the correction process. The correction process specifyingunit 52 may specify the ON of the correction process on one or morecolor components or may specify the OFF of the correction process on oneor more color components.

The correction amount calculating unit 44 includes an R-componentcorrection amount calculating section 44R, a G-component correctionamount calculating section 44G, and a B-component correction amountcalculating section 44B and calculates the correction amount of eachcolor component. The R-component correction amount calculating section44R, the G-component correction amount calculating section 44G, and theB-component correction amount calculating section 44B calculate thecorrection amount on the basis of the correction table selected by thecorrection table selecting unit 50.

The image signal correcting unit 46 includes an R-component image signalcorrecting section 46R, a G-component image signal correcting section46G, and a B-component image signal correcting section 468 and cancorrect the image signals of the respective color components. Thesection of which the ON is specified by the correction processspecifying unit 52 out of the R-component image signal correctingsection 46R, the G-component image signal correcting section 46G, andthe B-component image signal correcting section 46B performs acorrection process on the image signal of the corresponding colorcomponent using the correction amount calculated by the correspondingcolor-component correction amount calculating section. The section ofwhich the OFF is specified by the correction process specifying unit 52out of the R-component image signal correcting section 46R, theG-component image signal correcting section 46G, and the B-componentimage signal correcting section 46B does not perform a correctionprocess on the image signal of the corresponding color component.

By this configuration, the correction amount of the respective colorcomponents is calculated on the basis of the specified correction tableand the image signals are independently corrected among the colorcomponents.

The projection unit 100 is supplied with the image signals subjected tothe correction process by the image processor 30. The projection unit100 is constructed by, for example, a 3-panel liquid crystal projectorand projects an image onto the screen SCR on the basis of the imagesignals of the sub pixels constituting one pixel. More specifically, theprojection unit 100 modulates light from a light source not shown andprojects the modulated light onto the screen SCR on the basis of theimage signals corrected by the image processor 30.

FIG. 3 is a diagram illustrating the configuration of the projectionunit 100 shown in FIG. 1 In FIG. 3, the projection unit 100 in thisembodiment is constructed by the 3-panel liquid crystal projector, butthe projection unit of the image displaying apparatus according to theinvention is not limited to the 3-panel liquid crystal projector.

The projection unit 100 includes a light source 110, integrator lenses112 and 114, a polarization converting device 116, a superposing lens118, an R-component dichroic mirror 120R, a G-component dichroic mirror120G, a reflecting mirror 122, an R-component field lens 124R, aG-component field lens 124G, an R-component liquid crystal panel 130R(first light modulating device), a G-component liquid crystal panel 130G(second light modulating device), a B-component liquid crystal panel130B (third light modulating device), a relay optical system 140, across dichroic prism 160, and a projection lens 170. The liquid crystalpanels used as the R-component liquid crystal panel 130R, theG-component liquid crystal panel 130G, and the B-component liquidcrystal panel 130B are transmissive liquid crystal display devices. Therelay optical system 140 includes relay lenses 142, 144, and 146 andreflective mirrors 148 and 150.

The light source 110 includes, for example, an ultrahigh-pressuremercury lamp and emits light including at least an R-component beam, aG-component beam, and a B-component beam. The integrator lens 112includes plural small lenses for dividing the light from the lightsource 110 into plural partial beams. The integrator lens 114 includesplural small lenses corresponding to the small lenses of the integratorlens 112. The superposing lens 118 superposes the partial beams emittedfrom the small lenses of the integrator lens 112 on the liquid crystalpanels.

The polarization converting device 116 includes a polarization beamsplitter array and a λ/2 plate and converts the light from the lightsource 110 substantially into one kind of polarized light. Thepolarization beam splitter array has a structure in which a polarizationdividing film for dividing the partial beams divided by the integratorlens 112 into p-polarized beams and s-polarized beams and a reflectingfilm for changing the traveling direction of the light from thepolarization dividing film are alternately arranged. Two kinds ofpolarized beams divided by the polarization dividing film are arrangedto be equal in the polarization direction by the λ/2 plate. The lightconverted substantially into one kind of polarized light by thepolarization converting device 116 is input to the superposing lens 118.

The light from the superposing lens 118 is input to the R-componentdichroic mirror 120R. The R-component dichroic mirror 120R has afunction of reflecting the R-component beam and transmitting theG-component beam and the B-component beam. The light transmitted by theR-component dichroic mirror 120R is input to the G-component dichroicmirror 120G and the light transmitted by the R-component dichroic mirror1208 is reflected by the reflecting mirror 122 and guided to theR-component field lens 124R.

The G-component dichroic mirror 120G has a function of reflecting theG-component beam and transmitting the B-component beam. The lighttransmitted by the G-component dichroic mirror 120G is input to therelay optical system 140 and the light reflected by the G-componentdichroic mirror 120G is guided to the G-component field lens 124G.

In the relay optical system 140, the length difference between theoptical paths is corrected using the relay lenses 142, 144, and 146 soas to reduce the length difference between the optical path of theB-component beam transmitted by the G-component dichroic mirror 120G andthe optical paths of the R-component beam and the G-component beam so asto be as small as possible. The light passing through the relay lens 142is guided to the relay lens 144 by the reflecting mirror 148. The lightpassing through the relay lens 144 is guided to the relay lens 146 bythe reflecting mirror 150. The light passing through the relay lens 146is input to the B-component liquid crystal panel 130B.

The light input to the R-component field lens 124R is converted intoparallel light and is input to the R-component liquid crystal panel130R. The R-component liquid crystal panel 130R serves as a lightmodulating device (light modulating unit) and changes its transmittance(transmission rate, modulation rate) on the basis of the R-componentimage signal. Therefore, the light (first color-component beam) input tothe R-component liquid crystal panel 130R is modulated on the basis ofthe R-component image signal corrected by the image processor 30 and themodulated light is input to the cross dichroic prism 160.

The light input to the G-component field lens 124G is converted intoparallel light and is input to the G-component liquid crystal panel130G. The G-component liquid crystal panel 130G serves as a lightmodulating device (light modulating unit) and changes its transmittance(transmission rate, modulation rate) on the basis of the G-componentimage signal. Therefore, the light (second color-component beam) inputto the G-component liquid crystal panel 130G is modulated on the basisof the G-component image signal corrected by the image processor 30 andthe modulated light is input to the cross dichroic prism 160.

The B-component liquid crystal panel 130B to which the light convertedinto parallel light by the relay lenses 142, 144, and 146 is inputserves as a light modulating device (light modulating unit) and changesits transmittance (transmission rate, modulation rate) on the basis ofthe B-component image signal. Therefore, the light (thirdcolor-component beam) input to the B-component liquid crystal panel 130Bis modulated on the basis of the B-component image signal corrected bythe image processor 30 and the modulated light is input to the crossdichroic prism 160.

The R-component liquid crystal panel 1308, the O-component liquidcrystal panel 130G, and the B-component liquid crystal panel 130B havethe same configuration. Each liquid crystal panel is constructed bysealing a liquid crystal, as an electro-optical material, between a pairof transparent glass substrates and modulates the transmittance of thecolor-component beams in response to the image signals of the subpixels, for example, using a polysilicon thin film transistor as aswitching element.

The cross dichroic prism 160 has a function of outputting as an outputbeam a synthesized beam obtained by synthesizing the input beams fromthe R-component liquid crystal panel 130R, the O-component liquidcrystal panel 130G, and the B-component liquid crystal panel 130B. Theprojection lens 170 is a lens for extending and focusing the outputimage onto the screen SCR and has a function of extending or reducing animage in accordance with a zoom magnification.

The geometric correction and the pixel shift correction according tothis embodiment will be described now.

FIGS. 4A and 4B are diagrams illustrating the geometric correctionprocess according to this embodiment. FIG. 4A schematically shows pixels(sub pixels) of the R-component liquid crystal panel 130R. FIG. 4Bschematically shows an image displayed on the screen SCR using a beammodulated by the R-component liquid crystal panel 130R.

FIG. 5 is a diagram schematically illustrating the shape of a displayimage before and after the geometric correction in this embodiment.

For example, depending on the positional relation between the body ofthe projector 20 and the screen SCR as shown in FIG. 4A, the shape ofthe display image projected onto the screen SCR is distorted as shown inFIG. 4B. This results from, for example, the optical characteristic(geometric aberration) of the projection lens. Therefore, for example,the image signal of sub pixel P1 of FIG. 4A corresponding to display subpixel P2 of FIG. 4B is calculated by an interpolation process using theimage signals of one or more sub pixels (for example, a sub pixel groupP10 in FIG. 4A) around sub pixel P1 and is output as the image signal ofsub pixel P1 after the geometric correction. The R-component liquidcrystal panel 130R of the projection unit 100 modulates the light fromthe light source using the corrected image signal corresponding to subpixel P1 and projects the modulated light onto the screen SCR.

As a result, for example, the shape of the projection image IMG1 beforethe geometric correction is corrected to that of the projection imageIMG2 after the geometric correction as shown in FIG. 5 and it is thuspossible to display a proper display image depending on the positionalrelation between the projector 20 and the screen SCR.

Although the R-component display sub pixel is exemplified in FIGS. 4Aand 4B and FIG. 5, the same is true in the G component and the Bcomponent. Although the geometric correction due to the positionalrelation between the projector 20 and the screen SCR or the geometricaberration of the projection lens is exemplified, the same is true inthe case where the geometric correction is made due to the direction ofthe projection plane of the screen SCR about the projector 20.

In this way, the geometric correction is made due to, for example, thepositional relation between the body of the projector 20 and the screenSCR or the geometric aberration of the projection lens, but the pixelshift correction is made due to, for example, the installation precisionor the chromatic aberration of the optical components.

FIG. 6 is a diagram schematically illustrating a display pixel forming adisplay image projected onto the screen SCR by the projection unit 100shown in FIG. 3.

The display pixel PX forming the display image projected onto the screenSCR includes an R-component display sub pixel PR corresponding to thesub pixel of the R-component liquid crystal panel 130R, a G-componentdisplay sub pixel PG corresponding to the sub pixel of the G-componentliquid crystal panel 130G, and a B-component display sub pixel PBcorresponding to the sub pixel of the B-component liquid crystal panel130B. The projection unit 100 projects the light beams so as tosuperpose the R-component display sub pixel PR, the G-component displaysub pixel PG, and the B-component display sub pixel PB.

Since the projection unit 100 has the configuration shown in FIG. 3, theshift in the display position of a display sub pixel on the screen SCRmay occur due to the chromatic aberration of the optical system or theadjustment precision of positioning means of constituent members of theoptical system. Therefore, depending on the amount of pixel shift in thedisplay position of the display sub pixel, the image signal of the subpixel corresponding to the display sub pixel is calculated by theinterpolation process using the image signals of one or more sub pixelsaround the sub pixel and is output as the image signal of the sub pixelafter the correction of the pixel shift. Accordingly, even when theshift in the display position of a display sub pixel occurs, it ispossible to suppress the deterioration in resolution or the occurrenceof false colors, for example, in the edge portion or the end portion ofthe display image and thus to suppress the deterioration in imagequality of the display image.

Operations of the correction amount calculating unit 44 and the imagesignal correcting unit 46 performing the above-mentioned correctionprocess will be described now.

FIG. 7 is a diagram illustrating the operation of the R-componentcorrection amount calculating section 44R shown in FIG. 2.

Here, it is assumed that the correction table corresponding to theamount of pixel shift in the display position of the R-component displaysub pixel is stored in the correction table storage unit 40 and theR-component correction amount calculating unit 44R calculates thecorrection amount on the basis of the correction table. Although theR-component correction amount calculating section 44R is exemplified inFIG. 7, the same is true in the G-component correction amountcalculating section 44G and the B-component correction amountcalculating section 44B.

FIG. 7 shows a projection area PA of a display image (where the numberof pixels in the horizontal direction is W and the number of pixels inthe vertical direction is H) projected by the projection unit 100. Thecorrection table selected by the correction table selecting unit 50 outof the correction tables stored in the correction table storage unit 40includes correction data corresponding to the amounts of pixel shift inthe display position of the display sub pixels constituting displaypixels in or around four corners of the display image.

In FIG. 7, the amounts of pixel shift in the display position of theR-component display sub pixels PR1 to PR4 are schematically shown. Theamount of pixel shift includes an amount of pixel shift dx in the xdirection as the horizontal direction and an amount of pixel shift dy inthe y direction as the vertical direction. That is, the correction tablereferred to by the R-component correction amount calculating section 44Rincludes the amount of pixel shift dx[0] in the x direction and theamount of pixel shift dy[0] in the y direction as the amount of pixelshift in the display position of the display sub pixel PR1.

Here, it is preferable that the amount of pixel shift in the displayposition of the display sub pixel is normalized as follows.

FIG. 8 is a diagram illustrating the amounts of pixel shift in thedisplay position of the display sub pixels in this embodiment. In FIG.8, the same elements as shown in FIG. 7 are referenced by the samereference numerals and signs and the description thereof is properlyomitted.

The size of the projection area PA of the display image projected by theprojection unit 100 of the projector 20 is uniquely determined.Therefore, when the length of the projection area PA in the horizontaldirection is DLEN and the number of pixels in the horizontal directionis D, it can be specified to how many pixels the amount of pixel shiftin the x direction corresponds by calculating the amount of pixel shiftusing DLEN/D as a unit. Similarly, when the length of the projectionarea PA in the vertical direction is HLEN and the number of pixels inthe vertical direction is H, it can be specified to how many pixels theamount of pixel shift in the y direction corresponds by calculating theamount of pixel shift using HLEN/H as a unit.

By using the amount of pixel shift dx[0] and dy[0] of the display subpixel PR1, the amount of pixel shift dx[1] and dy[1] of the display subpixel PR2, the amount of pixel shift dx[2] and dy[2] of the display subpixel PR3, and the amount of pixel shift dx[3] and dy[3] of the displaysub pixel PR4, which are normalized, the R-component correction amountcalculating section 44R calculates the amount of pixel shift in the xdirection x_shift and the amount of pixel shift in the y directiony_shift of the display sub pixel PRE in the projection area PA.

More specifically, the R-component correction amount calculating section44R calculates the amount of pixel shift in the x direction x_shift(x,y)of the display sub pixel PRE located at the coordinate (x,y) using theleft-upper corner of the projection area PA on the basis of the amountsof pixel shift dx[0] to dx[3]. At this time, the R-component correctionamount calculating section 44R calculates the amount of pixel shiftx_shift(x,y) by a linear interpolation process expressed by thefollowing expression.

$\begin{matrix}{{{x{\_ shift}}\left( {x,y} \right)} = {{\left( {1 - \frac{y}{H - 1}} \right) \cdot \left\{ {{\left( {1 - \frac{x}{W - 1}} \right) \cdot {{dx}\lbrack 0\rbrack}} + {\left( \frac{x}{W - 1} \right) \cdot {{dx}\lbrack 1\rbrack}}} \right\}} + {\left( \frac{y}{H - 1} \right) \cdot \left\{ {{\left( {1 - \frac{x}{W - 1}} \right) \cdot {{dx}\lbrack 2\rbrack}} + {\left( \frac{x}{W - 1} \right) \cdot {{dx}\lbrack 3\rbrack}}} \right\}}}} & (1)\end{matrix}$

Similarly, the R-component correction amount calculating section 44Rcalculates the amount of pixel shift in the y direction y_shift(x,y) ofthe display sub pixel PRE located at the coordinate (x,y) using theleft-upper corner of the projection area PA on the basis of the amountsof pixel shift dy[0] to dy[3].

$\begin{matrix}{{{y\_ shift}\left( {x,y} \right)} = {{\left( {1 - \frac{x}{H - 1}} \right) \cdot \left\{ {{\left( {1 - \frac{y}{W - 1}} \right) \cdot {{dy}\lbrack 0\rbrack}} + {\left( \frac{y}{W - 1} \right) \cdot {{dy}\lbrack 1\rbrack}}} \right\}} + {\left( \frac{x}{H - 1} \right) \cdot \left\{ {{\left( {1 - \frac{y}{W - 1}} \right) \cdot {{dy}\lbrack 2\rbrack}} + {\left( \frac{y}{W - 1} \right) \cdot {{dy}\lbrack 3\rbrack}}} \right\}}}} & (2)\end{matrix}$

As described above, it is possible to calculate the correction amount tobe used in the correction of pixel shift in a unit smaller than onepixel by performing the interpolation process using the amounts of pixelshift at representative points. Therefore, it is possible to perform acorrection process with high precision and thus to further prevent thedeterioration in image quality.

Although it is exemplified in FIGS. 7 and 8 that the amounts of pixelshift of the R-component display sub pixels in the projection area PA,the amounts of pixel shift of the G-component display sub pixels and theB-component display sub pixels in the projection area PA can becalculated in the same way. Accordingly, even when the correction tablestorage unit 40 stores only the correction data corresponding to theamounts of pixel shift of four corners of the projection area PA used inthe pixel shift correcting process, the respective sections of thecorrection amount calculating unit 44 can calculate the amounts of pixelshift of all the display sub pixels in the projection area PA.

However, it is preferable that the correction tables referred to by thesections of the correction amount calculating unit 44, at the time ofcorrecting the pixel shift, include the correction data corresponding tothe amounts of pixel shift in display position of the R-componentdisplay sub pixels and the correction data corresponding to the amountsof pixel shift in display position of the B-component display sub pixelsrelative to the display positions of the G-component display sub pixels.In this case, the pixel shift correction process of the G-componentcorrection amount calculating section 44G can be omitted. When thesections of the correction amount calculating unit 44 calculate only thecorrection amounts used in the pixel shift correcting process, it ispossible to reduce the capacity of the correction table referred to bythe sections of the correction amount calculating unit 44.

Although it is exemplified in FIGS. 7 and 8 that the correction tablesstored in the correction table storage unit 40 include correction datacorresponding to the amounts of pixel shift in the display position ofthe display sub pixels constituting the display pixels in or around fourcorners of the display image, the embodiment is not limited to thisconfiguration. Only the correction data corresponding to the amounts ofpixel shift in the display position of plural display sub pixelscorresponding to plural sub pixels around the sub pixel of which thecorrection amount should be calculated can be included in the correctiontables stored in the correction table storage unit 40. For example, thecorrection data corresponding to the amounts of pixel shift of pluralrepresentative points in one line in the horizontal direction of thedisplay image or the correction data corresponding to the amounts ofpixel shift of plural representative points in one line in the verticaldirection of the display image may be included therein.

Although it is exemplified in FIGS. 7 and 8 that the sections of thecorrection amount calculating unit 44 calculate the correction amountsto be used in the pixel shift correcting process, the correction amountsto be used in the geometric correction process can be calculated in thesame way. In this case, at plural representative points in one screenthe correction tables stored in the correction table storage unit 40include the correction data corresponding to the amounts to be subjectedto the geometric correction and the sections of the correction amountcalculating unit 44 calculate the correction amounts to be used in thegeometric correction process as described above.

For example, the correction tables corresponding to the amounts of pixelshift in the display position of the display sub pixels and thegeometric correction amounts of the display image formed by the displaypixels can be stored in the correction table storage unit 40. In thiscase, for example, the summed value of the x component of the amount ofpixel shift and the x component of the geometric correction amount andthe summed value of the y component of the amount of pixel shift and they component of the geometric correction amount can be stored in thecorrection tables. The sections of the correction amount calculatingunit 44 can calculate the correction amounts on the basis of thecorrection table, thereby obtaining the correction amounts to be used inthe pixel shift correcting process and the correction amounts to be usedin the geometric correction process.

FIG. 9 is a diagram illustrating the operation of the R-component imagesignal correcting section 46R shown in FIG. 2.

Although the R-component image signal correcting section 46R is shown inFIG. 9, the same is true in the G-component image signal correctingsection 46G and the B-component image signal correcting section 46B.

FIG. 9 shows a process of correcting the pixel value IMGs[i][j] of thesub pixel R(i,j) corresponding to the R-component display sub pixel. InFIG. 9, R-component sub pixels around the R-component sub pixel R(i,j)defined in the coordinate system using the left-upper corner of theprojection area as an origin are schematically shown. Here, for example,the R-component sub pixel R(i−1,j−1) has a pixel value of img[i−1][j−1]and the R-component sub pixel R(i,j+1) has a pixel value of img[i][j+1].

The display position of the display sub pixel corresponding to the subpixel R(i,j) in FIG. 9 is shifted by an x_shift in the x direction andby a y_shift in the y direction from the display position of the displaysub pixel corresponding to the G-component sub pixel. The correctiondata (parameter) corresponding to this amount of pixel shift is readfrom the correction table stored in the correction table storage unit 40or is calculated by the R-component correction amount calculatingsection 44R described with reference to FIGS. 7 and 8.

The R-component image signal correcting section 46R calculates the pixelvalue IMGs[i][j] of the sub pixel R(i,j) by an area gray-scale methodusing the pixel values of the sub pixels (sub pixels adjacent in the xdirection and sub pixels adjacent in the y direction) around the subpixel R(i,j) on the basis of the correction data (parameter)corresponding to the amounts of pixel shift and outputs the pixel valueIMGs[i][j] as the corrected image signal to the projection unit 100.

IMGs[i][j]=(1−y_shift)·{(1−x_shift)·img[i][j]+x_shift·img[i+1][j]}+y_shift·{(1−x_shift)·img[i][j+1]+x_shift·img[i+1][j+1]}  (3)

The sections of the image signal correcting unit can correct the imagesignal of one sub pixel by interpolating the image signal of the one subpixel and the image signals corresponding to one or more sub pixelsaround the one sub pixel on the basis of the correction tables.Accordingly, it is possible to correct the pixel shift in a unit smallerthan one pixel and thus to perform a correction process with highprecision.

When the correction data included in the correction tables is thecorrection data corresponding to the geometric correction amounts, it ispossible to correct the image signal of the sub pixel so as to make ageometric correction of the display image by the above-mentionedinterpolation process. When the correction data included in thecorrection tables is the correction data corresponding to the amounts ofpixel shift, it is possible to correct the pixel shift of thecorresponding sub pixel by the interpolation process. When thecorrection data included in the correction table is the correction datacorresponding to the geometric correction amounts and the amounts ofpixel shift, it is possible to geometrically correct the sub pixel andto correct the pixel shift of the sub pixel.

The function of the image processor 30 for correcting the image signalcorresponding to the sub pixel on the basis of the correction tablesstored in the correction table storage unit 40 may be embodied byhardware or may be embodied by software.

FIG. 10 is a block diagram illustrating a hardware configuration of theimage processor 30 according to this embodiment.

The image processor 30 includes a central processing unit (CPU) 80, aread only memory (ROM) 82, a random access memory (RAM) 84, an interface(I/F) circuit 86, and an image processing circuit 88. The CPU 80, theROM 82, the RAM 84, the I/F circuit 86, and the image processing circuit88 are connected to each other via a bus 90.

The ROM 82 stores programs and the CPU 80 reading the programs via thebus 90 can perform processes corresponding to the programs. The RAM 84serves as a work area for the CPU 80 or temporarily stores the programsread by the CPU 80. The I/F circuit 86 performs an interface process ofinputting image signals from the outside or an interface process ofoutputting image signals to the projection unit 100.

The CPU 80 reads the programs stored in the ROM 82 or the RAM 84 andperforms the processes corresponding to the programs. The imageprocessing circuit 88 performs a process of correcting the image signalscorresponding to the sub pixels on the basis of control data specifiedby the CPU 80.

The function of the correction table storage unit 40 shown in FIG. 2 isembodied by the ROM 82 or the RAM 84. The functions of the correctionamount calculating unit 44, the image signal correcting unit 46, thecorrection table selecting unit 50, and the correction processspecifying unit 52 shown in FIG. 2 are embodied by the image processingcircuit 88. The CPU 80 reads the programs stored in the ROM 82 or theRAM 84 via the bus 90 and controls the image processing circuit 88 bysetting the control data in the correction process specifying unit 52 inaccordance with the programs. An image signal acquiring unit not shownin FIGS. 1 and 2 has a function of buffering input image signalssupplied from the outside and this function is embodied by, for example,the RAM 84 or the I/F circuit 86 shown in FIG. 10.

In this embodiment, 3 (=N) types of correction tables in maximum can beallocated to a definite correction table storage area in the memory areaof the ROM 82 or the RAM 84. In this embodiment, various correctionprocesses can be performed with a simple configuration depending on thenumber of types of correction tables allocated in the correction tablestorage area.

First Processing Example

FIG. 11 is a diagram illustrating an example where the correction tablestorage area is allocated in a first processing example of thisembodiment.

FIG. 11 shows an example where the entire area of the correction tablestorage area of the ROM 82 or the RAM 84 as the correction table storageunit 40 is allocated as a correction table storage area common to the Rcomponent, the G component, and the B component. That is, the firstprocessing example is an example where the correction table storage unit40 stores only one type of correction table.

In the first processing example, the same correction process can belocally or totally carried out on the R component, the G component, andthe B component constituting one pixel. Therefore, the correction tablein the first processing example can be constructed by correction datacorresponding to the amounts of geometric correction.

In the following description, it is exemplified that the screen SCR is aso-called cylindrical screen and the shape of an image projected ontothe cylindrical screen is corrected as the geometric correction.

FIGS. 12A and 12B are diagrams illustrating the shape correction of theimage projected onto the cylindrical screen. FIG. 12A is a diagramillustrating the cylindrical screen. FIG. 12B is a top view of FIG. 12A.In FIGS. 12A and 12B, the same portions as shown in FIG. 1 arereferenced by the same reference numerals and signs and the descriptionthereof is properly omitted. The cylindrical screen shown in FIG. 12Bindicates the top view of an image projection area of the cylindricalscreen shown in FIG. 12A and ends of the cylindrical screen shown inFIG. 12B indicate the ends of a projected image.

In FIGS. 12A and 12B, a point of view V is located at the center of thecylindrical screen with a radius R and the projector 20 is installed ata position backwardly apart by L from the point of view V. The width inthe horizontal direction of the cylindrical screen as viewed from thepoint of view V is 2w. Here, when the projector 20 projects an imageonto the cylindrical screen shown in FIGS. 12A and 12B, the shape of theimage projected from the projector 20 and the shape of the image viewedfrom the point of view V are not matched with each other due to theprojection surface of the cylindrical screen.

For example, when a pixel P on the cylindrical screen in the directioninclined by angle θ about the right front of the projector 20 and thepoint of view V is viewed from the point of view V, the pixel isrecognized as a pixel located at an intersection Q1 on a virtual screenplane connecting both ends in the horizontal direction of thecylindrical screen. Accordingly, the projector 20 needs to project thepixel located at the intersection Q1 to an intersection Q2 of a lineconnecting the pixel P and the projector 20 and the screen plane.Therefore, the projector 20 displays an image obtained by shifting anoriginal image by a correction amount Δx (distance between theintersection Q1 and the intersection Q2) in the horizontal direction.

Here, Δx is expressed by the following expression and the correctiontables preferably include the correction data corresponding to thecorrection amount calculated by the following expression.

$\begin{matrix}{{\Delta \; x} = {\frac{{R\left( {L + \sqrt{R^{2} - w^{2}}} \right)}\; {\sin \theta}}{{R\; {cos\theta}} + L} - {\sqrt{{R^{2} - w^{2}}\;}{tan\theta}}}} & (4)\end{matrix}$

FIG. 13 shows the correction amount of FIG. 12B. In FIG. 13, thehorizontal axis represents the number of pixels (distance) from thecenter of the cylindrical screen and the vertical axis represents thecorrection amount Δx.

As shown in FIG. 13, in the first processing example, the correctiondata corresponding to such a correction amount Δx that the correctionamount Δx at the center of the cylindrical screen and at the edges ofthe cylindrical screen is “0” and the correction amount Δx becomesgreater in the vicinity of the middle pixel thereof is included in thecorrection table.

FIG. 14 is a flowchart illustrating the processes of the image processor30 in the first processing example of this embodiment.

For example, a program for embodying the processes shown in FIG. 14 isstored in the ROM 82 in advance and the processes shown in FIG. 14 canbe embodied by software by allowing the CPU 80 to read the programstored in the ROM 82 and to perform the processes corresponding to theprogram.

First, as a correction process ON/OFF setting step performed by thecorrection process specifying unit of the image processor 30, the CPU 80sets the correction process of the RGB color components in the imageprocessing circuit 88 to ON (step S10). Accordingly, the image processor30 performs the image signal correcting process on the respective RGBcolor components.

As a correction table reference destination specifying step in thecorrection process specifying unit 52 of the image processor 30, the CPU80 specifies which of the first to third correction tables 42 ₁ to 42 ₃stored in the correction table storage unit 40 the image processingcircuit 88 should refer to for each of the RGB color components (stepS12). Here, a single correction table common to the RGB color componentsshould be referred to.

As an input image signal acquiring step, the image processor 30 acquiresimage signals corresponding to the sub pixels constituting the pixels ofthe input image from an image signal generating device not shown (stepS14).

As a correction data acquiring step in the correction table selectingunit 50 of the image processor 30, the correction data of the respectivecolor components are acquired on the basis of the correction tablecommon to the RGB color components and specified in step S12 (step S16).

As a correction amount calculating step in the correction amountcalculating unit 44 of the image processor 30, the sections of thecorrection amount calculating unit 44 calculate the correction amountsof the color components (step S18). In step S18, the correction amountsof the color components are calculated as described with reference toFIG. 7 on the basis of the correction data corresponding to thecorrection amounts shown in FIG. 13.

As an image signal correcting step in the image signal correcting unit46 of the image processor 30, the sections of the image signalcorrecting unit 46 correct the image signals by the color componentsusing the correction amounts calculated in step S18 (step S20). In stepS20, the image signals are corrected by the color components asdescribed with reference to FIG. 9.

This series of processes are ended when the image signal correctingprocess is performed on all the pixels (Y in step S22) and the processof step S14 is performed again when the image signal correcting processis not performed on all the pixels (N in step S22).

The image signals corrected in this way are input to the projection unit100. As an image displaying step, the projection unit 100 projects themodulated light onto the screen SCR on the basis of the image signalscorrected by the image processor 30 to display an image.

As described above, in the first processing example, the entire area ofthe correction table storage area of the ROM 82 or the RAM 84 as thecorrection table storage unit 40 is allocated as the correction tablestorage area common to the R component, the G component, and the Bcomponent. Accordingly, it is possible to perform the correction processcommon to the RGB color components while utilizing the memory capacityof the correction data to the maximum. Since the memory capacity of thecorrection data can be utilized to the maximum, it is possible toperform the correction process with higher precision and to correct withhigher precision, for example, the shape of an image projected onto thecylindrical screen. The geometric correction in the first processingexample may be a local geometric correction of a proximal projector, orthe like.

Although it has been described in the first processing example that onlythe geometric correction is carried out without making a correction ofthe pixel shift, this embodiment is not limited to this configuration.For example, by allowing one correction table to include only thecorrection data corresponding to the amounts of pixel shift in displayposition of the R-component and B-component display sub pixels relativeto the display position of the G-component display sub pixel, settingthe process of correcting the G-component image signal and the processof correcting the B-component image signal having relatively-low eyesensitivity to OFF, and performing the process of correcting theR-component image signal, it is possible to precisely perform the pixelshift correcting process of the R component.

Second Processing Example

FIG. 15 is a diagram illustrating an example where the correction tablestorage area is allocated in a second processing example of thisembodiment.

In FIG. 15, the correction table storage area of the ROM 82 or the RAM84 as the correction table storage unit 40 is divided into two areas andis allocated as an R-component correction table storage area and aB-component correction table storage area. That is, in the secondprocessing example, the correction table storage unit 40 stores only twokinds of correction tables.

In the second processing example, it is possible to correct the pixelshifts of the R component and the B component relative to the displayposition of the G-component display sub pixel out of the R-component,G-component, and B-component display sub pixels constituting one pixel.Accordingly, the correction table in the second processing example canbe constructed by the correction data corresponding to the correctionamount of the pixel shift.

FIG. 16 is a diagram illustrating an example of the correction amount ofthe pixel shift of the R component in the second processing example. InFIG. 16, the horizontal axis represents the number of pixels (distance)from the center of the screen and the vertical axis represents thecorrection amount of pixel shift Δx. In FIG. 16, plural amounts of pixelshift in the horizontal direction from the center of the screen isgiven, but only the amounts of the pixel shift of four corners of thedisplay image may be given as described with reference to FIG. 7.

In the second processing example, the correction data corresponding tothe correction amount Δx shown in FIG. 16 is stored in the correctiontable depending on the number of pixels from the center of the screen.In FIG. 16, the pixel shift amount distribution in the horizontaldirection of the image is shown, but the amounts of pixel shift in thevertical direction of the image may be included in the correction tabledepending on the number of pixels from the center of the screen.

FIG. 17 is a flowchart illustrating the processes of the image processor30 in the second processing example of this embodiment. In FIG. 17, itis assumed that the scanning lines in the horizontal direction of thedisplay image have the same amounts of pixel shift in the horizontaldirection as shown in FIG. 16 and the scanning lines in the verticaldirection have the same pixel shift amount distribution in the verticaldirection as shown in FIG. 16.

For example, a program for embodying the processes shown in FIG. 17 isstored in the ROM 82 in advance and the processes shown in FIG. 17 canbe embodied by software by allowing the CPU 80 to read the programstored in the ROM 82 and to perform the processes corresponding to theprogram.

First, as the correction process ON/OFF setting step performed by thecorrection process specifying unit of the image processor 30, the CPU 80sets the correction process of the G component in the image processingcircuit 88 to OFF and sets the correction process of the R and Bcomponents to ON (step S30). Accordingly, the image processor 30performs the image signal correcting process on the R component and theB component.

As the correction table reference destination specifying step in thecorrection process specifying unit 52 of the image processor 30, the CPU80 specifies which of the first and second correction tables 42 ₁ and 42₂ stored in the correction table storage unit 40 the image processingcircuit 88 should refer to for each of the R and B components (stepS32). Here, different correction tables should be referred to for the Rcomponent and the B component, respectively.

As the input image signal acquiring step, the image processor 30acquires image signals corresponding to the sub pixels constituting thepixels of the input image from an image signal generating device notshown (step S34).

As the correction data acquiring step in the correction table selectingunit 50 of the image processor 30, the correction data of the respectivecolor components are acquired on the basis of the correction tablesrespectively specified for the R component and the B component in stepS32 (step S36).

As the correction amount calculating step in the correction amountcalculating unit 44 of the image processor 30, the R-componentcorrection amount calculating section 44R and the B-component correctionamount calculating section 44B of the correction amount calculating unit44 calculate the correction amounts of the color components (step S38).In step S38, the correction amounts of the color components arecalculated by the interpolation process on the basis of the correctiondata corresponding to the correction amounts at the representativepoints shown in FIG. 16.

As an image signal correcting step in the image signal correcting unit46 of the image processor 30, the R-component image signal correctingsection 46R and the B-component image signal correcting section 46B ofthe image signal correcting unit 46 correct the image signals by thecolor components using the correction amounts calculated in step S38(step S40). In step S40, the image signals are corrected by the colorcomponents as described with reference to FIG. 9.

This series of processes are ended when the image signal correctingprocess is performed on all the pixels (Y in step S42) and the processof step S34 is performed again when the image signal correcting processis not performed on all the pixels (N in step S42).

The image signals corrected in this way are input to the projection unit100. As an image displaying step, the projection unit 100 projects themodulated light onto the screen SCR on the basis of the image signalscorrected by the image processor 30 to display an image.

As described above, in the second processing example, the correctiontable storage area of the ROM 82 or the RAM 84, as the correction tablestorage unit 40, is divided and allocated as the R-component correctiontable storage area and the B-component correction table storage area.That is, when one pixel includes N sub pixels, the correction tablestorage unit 40 stores (N−1) types of correction tables of which eachincludes the correction data corresponding to the amount of pixel shiftin the display position of the display sub pixel and the image signalcorrecting unit 46 independently corrects the image signals of (N−1)types of color components among the color components.

In the second processing example, since the correction table storagearea is divided into two storage areas, the memory capacity of thecorrection data of the respective correction tables can be reduced incomparison with the first processing example, and it is possible to makea correction of two color components every color component with a simplestructure. As a result, relative to the display position of the displaysub pixel of one color component, it is possible to correct the pixelshift corresponding to the amount of pixel shift in the display positionof the display sub pixels of the other color components.

It has been described in the second processing example that the pixelshift correcting process is performed using the G component as areference, the R component or the B component may also be used as thereference. That is, one of plural color components constituting onepixel may be used as the reference.

Third Processing Example

FIG. 18 is a diagram illustrating an example where the correction tablestorage area is allocated in a third processing example of thisembodiment.

In FIG. 18, the correction table storage area of the ROM 82 or the RAM84 as the correction table storage unit 40 is divided into three areasand is allocated as an R-component correction table storage area, aG-component correction table storage area, and a B-component correctiontable storage area. That is, in the third processing example, thecorrection table storage unit 40 stores three kinds of correctiontables.

In the third processing example, it is possible to independently correctthe pixel shifts of the R-component, G-component, and B-componentdisplay sub pixels constituting one pixel among the color components.Accordingly, the correction table in the third processing example can beconstructed by the correction data corresponding to the geometriccorrection amount and the correction amount of the pixel shift.

FIG. 19 is a diagram illustrating an example of the correction amount ofpixel shift in the third processing example. In FIG. 19, the horizontalaxis represents the number of pixels (distance) from the center of thescreen and the vertical axis represents the correction amount of pixelshift Δx.

In FIG. 19, the geometric correction amount AMD1 shown in FIG. 13 andthe correction amount AMD2 in the third processing example are showntogether. The correction amount AMD2 in the third processing example isacquired, for example, by adding the geometric correction amount shownin FIG. 13 and the correction amount of pixel shift shown in FIG. 16.

In the third processing example, the correction data corresponding tothe correction amount AMD2 shown in FIG. 19 is stored in the correctiontable depending on the number of pixels from the center of the screen.In FIG. 19, the correction amount of only one color component is shown,but the correction amount distributions are given for the other colorcomponents and the correction data corresponding to the correctionamount distributions are included in the correction table.

FIG. 20 is a flowchart illustrating the processes of the image processor30 in the third processing example of this embodiment. In FIG. 20, it isassumed that the scanning lines in the horizontal direction of thedisplay image have the same amounts of pixel shift in the horizontaldirection, as shown in FIG. 19, and the scanning lines in the verticaldirection have the same pixel shift amount distribution in the verticaldirection as shown in FIG. 19.

For example, a program for embodying the processes shown in FIG. 20 isstored in the ROM 82 in advance and the processes shown in FIG. 20 canbe embodied by software by allowing the CPU 80 to read the programstored in the ROM 82 and to perform the processes corresponding to theprogram.

First, as the correction process ON/OFF setting step performed by thecorrection process specifying unit of the image processor 30, the CPU 80sets the correction process of the RGB color components in the imageprocessing circuit 88 to ON (step S50). Accordingly, the image processor30 performs the image signal correcting process on the RGB colorcomponents.

As the correction table reference destination specifying step in thecorrection process specifying unit of the image processor 30, the CPU 80specifies different correction tables of the first to third correctiontables 42 ₁ to 42 ₃ stored in the correction table storage unit 40 whichthe image processing circuit 88 should refer to for each of the R, G,and B components (step S52). For example, the R component is referred tothe first correction table 42 ₁, the G component is referred to thesecond correction table 42 ₂, and the B component is referred to thethird correction table 42 ₃.

As the input image signal acquiring step, the image processor 30acquires image signals corresponding to the sub pixels constituting thepixels of the input image from an image signal generating device notshown (step S54).

As the correction data acquiring step in the correction table selectingunit 50 of the image processor 30, the correction data of the respectivecolor components are acquired on the basis of the correction tablesrespectively specified for the R component, the G component, and the Bcomponent in step S52 (step S56).

As the correction amount calculating step in the correction amountcalculating unit 44 of the image processor 30, the sections of thecorrection amount calculating unit 44 calculate the correction amountsof the color components (step S58). In step S58, the correction amountsof the color components are calculated on the basis of the correctiondata corresponding to the correction amounts shown in FIG. 19.

As an image signal correcting step in the image signal correcting unit46 of the image processor 30, the sections of the image signalcorrecting unit 46 correct the image signals by the color componentsusing the correction amounts calculated in step S58 (step S60). In stepS60, the image signals are corrected by the color components asdescribed with reference to FIG. 9.

This series of processes are ended when the image signal correctingprocess is performed on all the pixels (Y in step S62) and the processof step S54 is performed again when the image signal correcting processis not performed on all the pixels (N in step S62).

The image signals corrected in this way are input to the projection unit100. As an image displaying step, the projection unit 100 projects themodulated light onto the screen SCR on the basis of the image signalscorrected by the image processor 30 to display an image.

As described above, in the third processing example, the correctiontable storage area of the ROM 82 or the RAM 84 as the correction tablestorage unit 40 is divided and allocated as the R-component correctiontable storage area, the G-component correction table storage area, andthe B-component correction table storage area. That is, when one pixelincludes N sub pixels, the correction table storage unit 40 stores Ntypes of correction tables of which each includes the correction datacorresponding to the amount of pixel shift in the display position ofthe display sub pixel and the geometric correction amount of the displayimage constructed by the display pixel, and the image signal correctingunit 46 independently corrects the image signals among the colorcomponents on the basis of the correction tables which differ dependingon the color components.

In the third processing example, since the correction table storage areais divided into three storage areas, the memory capacity of thecorrection data of the respective correction tables can be reduced incomparison with the first and second processing examples, and it ispossible to make a correction of three color components with a simplestructure. As a result, it is possible to make both a correction ofpixel shift and a geometric correction for each color component.

As described above, in this embodiment, the correction table storageunit storing one or more correction tables is provided, and thegeometric correction of the display image formed by the display pixelsdisplayed so as to superpose the display sub pixels corresponding to thesub pixels is performed on the image signals of the color componentsindependently among the color components on the basis of the correctiontables stored in the correction table storage unit. Therefore, byreferring the color components to different correction tables, referringthe color components to the correction tables common to the plural colorcomponents, or referring all the color components to the commoncorrection table, it is possible to embody various correction processeswith a simple configuration. Accordingly, by storing, for example, thecorrection tables corresponding to the amount of pixel shift in thedisplay position of the display sub pixels and the geometric correctionamount of the display image constructed by the display pixels, it ispossible to make both a geometric correction of the display image and acorrection of the pixel shift corresponding to the amount of pixel shiftwith a simple configuration, thereby reducing the delay time of theimaging process.

Although the image processing apparatus, the image displaying apparatus,and the image processing method according to the invention have beendescribed with reference to the embodiment, the invention is not limitedto the embodiment but may be modified in various forms without departingfrom the spirit and scope of the invention. For example, the inventionmay be modified as follows.

(1) Although it has been described in the above-mentioned embodimentthat the correction table stored in the correction table storage unitincludes the correction data corresponding to the amount of pixel shiftof plural sub pixels sampled as representative points out of all thepixels in the display image and the correction amount calculating unitcalculates the amount of pixel shift of a sub pixel, the invention isnot limited to this configuration. For example, the correction tablestored in the correction table storage unit may include the correctiondata corresponding to the amount of pixel shift of the entire screen andthe correction amount calculating unit may be omitted.

(2) Although it has been described in the above-mentioned embodimentthat the correction table stored in the correction table storage unitincludes the correction data corresponding to the correction amount, theinvention is not limited to this configuration. For example, thecorrection table stored in the correction table storage unit may includethe correction amount itself.

(3) Although it has been described in the above-mentioned embodimentthat three sub pixels of three color components constitute one pixel,the invention is not limited to this configuration. The number of colorcomponents constituting one pixel may be 2 or 4 or more.

(4) Although it has been described in the above-mentioned embodimentthat the display position of one display sub pixel out of the displaysub pixels constituting each display pixel is used as the referenceposition for the pixel shift correction amount, the invention is notlimited to this configuration. For example, a predetermined position ina screen coordinate system or a predetermined position in a panelcoordinate system of the liquid crystal panels may be used as thereference position.

(5) Although it has been described in the above-mentioned embodimentthat a transmissive liquid crystal panel is used as the light modulatingdevice, the invention is not limited to this configuration. For example,a DLP (Digital Light Processing) (registered trademark) or an LCOS(Liquid Crystal On Silicon) may be employed as the light modulatingdevice.

(6) Although it has been described in the above-mentioned embodimentthat a so-called 3-panel transmissive liquid crystal panel is employedas the light modulating device, a 2- or 4- or more-panel transmissiveliquid crystal panel may be employed.

(7) The method of interpolating the amount of pixel shift of all the subpixels and the method of correcting the image signals according to theinvention are not limited to those described in the above-mentionedembodiment, but various methods such as a bi-linear method, a nearestneighboring method, a bi-cubic method, and an area gray-scale method maybe employed, which the invention is not also limited to.

(8) Although it has been described in the above-mentioned embodimentthat the invention is embodied as the image processing apparatus, theimage displaying apparatus, and the image processing method, theinvention is not limited to them. For example, the invention may beembodied as a recording medium on which a program describing a processsequence of the image processing method according to the invention isrecorded.

The entire disclosure of Japanese Patent Application No. 2008-252668,filed Sep. 30, 2008 is expressly incorporated by reference herein.

1. An image processing apparatus for correcting image signalscorresponding to a plurality of color images constituting an image,comprising: a correction table storage unit storing one or morecorrection tables; and an image signal correcting unit independentlycorrecting the image signals of the color images on the basis of one ormore correction tables stored in the correction table storage unit,wherein the image signal correcting unit makes a geometric correction ofa display image corresponding to the image such that display colorimages each corresponding to the color images superpose each other,independently among the color image.
 2. The image processing apparatusaccording to claim 1, wherein the correction table storage unit stores acorrection table including correction data corresponding to an amount ofpixel shift in the display position of the display color image and ageometric correction amount of the display image, and wherein the imagesignal correcting unit corrects the image signals so as to make ageometric correction of the display image and corrects the pixel shiftto correspond to the amount of pixel shift.
 3. The image processingapparatus according to claim 2, wherein the image signal correcting unitcorrects the image signal of sub pixel constituting the color image tomake a geometric correction of the display image and corrects the pixelshift by interpolating the image signal of the one sub pixel and theimage signals corresponding to one or more sub pixels around the one subpixel on the basis of the correction table.
 4. The image processingapparatus according to claim 1, wherein when one pixel is constructed byN (where N is an integer of 2 or greater) sub pixels, the correctiontable storage unit stores N types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels and thegeometric correction amount of the display image, and wherein the imagesignal correcting unit independently corrects the image signals amongthe color image on the basis of the correction tables which differdepending on the color image.
 5. The image processing apparatusaccording to claim 1, wherein when one pixel is constructed by N (whereN is an integer of 2 or greater) sub pixels, the correction tablestorage unit stores (N−1) types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels, andwherein the image signal correcting unit independently corrects theimage signals among the (N−1) types of color images.
 6. The imageprocessing apparatus according to claim 1, wherein when an image isdisplayed on a cylindrical screen with a radius R by an image displayingapparatus disposed backwardly apart by L from a point of view located atthe center of the cylindrical screen, one correction table stored in thecorrection table storage unit includes correction data of an angle θ bythe use of the following expression,${\Delta \; x} = {\frac{{R\left( {L + \sqrt{R^{2} - w^{2}}} \right)}\; {\sin \theta}}{{R\; {cos\theta}} + L} - {\sqrt{{R^{2} - w^{2}}\;}{tan\theta}}}$where 2w represents the width in the horizontal direction of thecylindrical screen as viewed from the point of view and Δx representscorrection data for the sub pixel in the direction of the angle θ fromthe point of view.
 7. An image displaying apparatus for displaying animage on the basis of image signals corresponding to a plurality ofcolor images constituting the image, comprising: the image processingapparatus according to claim 1; and an image displaying unit making adisplay to superpose display color images corresponding to the colorimage on the basis of the image signals corrected by the imageprocessing apparatus.
 8. An image processing method of correcting imagesignals corresponding to a plurality of color images constituting animage, comprising: acquiring the image signals corresponding to thecolor images; and correcting the acquired image signals independentlyamong the color images on the basis of one or more correction tablesstored in a correction table storage unit, wherein the correcting of theimage signals includes making a geometric correction of a display imagecorresponding to the image such that display color images eachcorresponding to the color images superpose each other, independentlyamong the color image.
 9. The image processing method according to claim8, wherein the correction table storage unit stores a correction tableincluding correction data corresponding to an amount of pixel shift inthe display position of the display color image and a geometriccorrection amount of the display image, and wherein the correcting ofthe image signals includes correcting the image signals so as to make ageometric correction of the display image and correcting the pixel shiftto correspond to the amount of pixel shift.
 10. The image processingmethod according to claim 9, wherein the correcting of the image signalsincludes making a geometric correction of the image signal of sub pixelconstituting the color image and correcting the pixel shift byinterpolating the image signal of the one sub pixel and the imagesignals corresponding to one or more sub pixels around the one sub pixelon the basis of the correction table.
 11. The image processing methodaccording to claim 8, wherein when one pixel is constructed by N (whereN is an integer of 2 or greater) sub pixels, the correction tablestorage unit stores N types of correction tables of which eachcorrection table includes correction data corresponding to the amount ofpixel shift in the display position of the display sub pixels and thegeometric correction amount of the display image, and wherein thecorrecting of the image signals includes independently correcting theimage signals among the color image on the basis of the correctiontables which differ depending on the color image.
 12. The imageprocessing method according to claim 8, wherein when one pixel isconstructed by N (where N is an integer of 2 or greater) sub pixels, thecorrection table storage unit stores (N−1) types of correction tables ofwhich each correction table includes correction data corresponding tothe amount of pixel shift in the display position of the display subpixels, and wherein the correction of the image signals includesindependently correcting the image signals among the (N−1) types of thecolor image.
 13. The image processing method according to claim 8,wherein when an image is displayed on a cylindrical screen with a radiusR by an image displaying apparatus disposed backwardly apart by L from apoint of view located at the center of the cylindrical screen, acorrection table stored in the correction table storage unit includescorrection data on an angle θ by the use of the following expression,${\Delta \; x} = {\frac{{R\left( {L + \sqrt{R^{2} - w^{2}}} \right)}\; {\sin \theta}}{{R\; {cos\theta}} + L} - {\sqrt{{R^{2} - w^{2}}\;}{tan\theta}}}$where 2w represents the width in the horizontal direction of thecylindrical screen as viewed from the point of view and Δx representscorrection data for the sub pixel in the direction of the angle θ fromthe point of view.